An image-forming process using silver halide photographic light-sensitive materials generally involves the main steps of development, fixing (or bleaching and fixing), and the like. In the developing step, developing agents well known in the art (for example, compounds as described in The Theory of the Photographic Processes, 4th Ed., compiled by T. H. James, pp. 298-324) dissolved in an alkaline aqueous solution are usually used as developing solutions.
Such developing solutions are unstable and are easily oxidized with dissolved oxygen or the like. Therefore, preservatives are added thereto to prevent oxidation. However, the developing solutions are so unstable in composition that their preservation is difficult. Recently, therefore, a technique of incorporating a developing agent in a silver halide light-sensitive material has been proposed.
Incorporation of a developing agent in a light-sensitive material makes it possible to simplify the composition of a processing solution. This facilitates the aforesaid preservation of a developing solution and is, in addition, advantageous for simplifying or accelerating the processing because the development can be fundamentally conducted in an alkaline bath.
Therefore, it has conventionally been attempted to incorporate a developing agent in a light-sensitive material. For example, photographic elements in which a black-and-white developing agent is incorporated in a light-sensitive material are described in U.S. Pat. Nos. 2,751,297, 3,902,905, 4,209,580, etc.
In general, however, incorporation of a developing agent as such in a light-sensitive material causes the developing agent to be oxidized in a comparatively short time. Further, problems such as desensitization, fogging, staining, etc., are liable to be caused during storage of the light-sensitive material and the developing agent loses its power to give only insufficient image density.
One technique proposed for removing these defects is to incorporate a developing agent precursor in a light-sensitive material. This precursor does not possess developing power during storage, and, hence, does not undergo oxidation and, only when brought into contact with a suitable activator (for example, alkalis, nucleophilic reagents, etc.), it produces a silver halide developing agent.
As such precursors, U.S. Pat. No. 3,295,978 describes salts of metals (lead, cadmium, calcium, barium, etc.) of hydroquinone, catechol, etc., U.S. Pat. No. 3,246,988 describes acyl halide derivatives of hydroquinone, U.S. Pat. No. 3,462,266 describes oxazine derivatives of hydroquinone, U.S. Pat. No. 3,615,512 describes lactone type developing agent precursors, British Pat. No. 1,258,924 describes hydroquinone presursors having a quaternary ammonium group, and British Pat. No. 1,023,701 describes acyl derivatives of 1-phenyl-3-pyrazolidinone.
However, these conventional developing agent precursors have the defect that some of them gradually release a developing agent during storage which is then oxidized, making it less effective, causing desensitization or fogging or to form a colored product, and others undergo a too slow decomposition upon desired development to produce a developing agent, thus having been unsatisfactory. That is, conventional developing agent precursors do not fully satisfy the following two requirements:
(1) Sufficiently stable against decomposition and oxidative deterioration during storage not to release a developing agent or form other compound; and
(2) capable of releasing a developing agent upon desired development processing in a short time in comparison with the developing time.